The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An engine appropriately mixes air and fuel and generates driving power by burning the mixed gas.
In order to output desired power and combustion efficiency, sufficient air should be supplied to the engine. For this, a turbocharger is used to increase combustion efficiency and supply sufficient air to the engine.
Generally, a turbine of the turbocharger is rotated by pressure of exhaust gas exhausted from the engine, a compressor of the turbocharger compresses fresh air flowing in from the outside, and the compressed air is supplied to a cylinder of the engine. The turbocharger has been applied to most diesel engines, and has recently been applied to gasoline engines.
As another example, there is an electric supercharger that compresses external air using a compressor operated by a motor. Since the electric supercharger is operated by the motor, there is little turbo lag. The electric supercharger mainly supplies compressed air to the cylinder in a low speed and low load region.
We have discovered that since the turbocharger (hereinafter referred to as a ‘mechanical turbocharger’) operated by exhaust gas has low responsiveness, there is a problem in realizing an engine having a high compression ratio because of high back pressure. Also, since the turbocharger is exposed to high temperature exhaust gas (i.e., Celsius 700 degrees), design cost of peripheral parts of the turbocharger is increased.
Further, since the output power of the motor is limited according to an output of a battery provided in a vehicle, the usage of the electric supercharger is limited to low and middle speed regions.